1. Field of the Invention
The present invention relates to a lens barrel, and more particularly to a telescopic lens barrel that holds a lens so as to be advanced and retracted in an optical axis direction of the lens barrel.
2. Description of the Related Art
In recent years, image pickup apparatuses such as digital still cameras or digital video cameras have been required to have higher portability or usability, and the entire apparatus has been reduced in size.
Also, the size of a lens barrel of a telescopic type or the like used in the image pickup apparatus has been reduced in size. In this case, there is a strong desire for higher image quality and higher pixelation, and it is desired to reduce the size of the lens barrel of the telescopic type or the like without reducing the size of a lens as an optical component. The telescopic lens barrel is disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2008-185786 and Japanese Laid-Open Patent Publication (Kokai) No. 2006-243569.
An increasing number of the telescopic lens barrels have been reported including a guide shaft that is placed outside a fixed cylinder for guiding a lens so as to be advanced and retracted in an optical axis direction of the lens barrel, for reduction in size. In this case, the guide shaft is required to be positioned with high accuracy and secured in order to advance and retract the lens in the optical axis direction with high accuracy.
However, in a first conventional lens barrel in Japanese Laid-Open Patent Publication (Kokai) No. 2008-185786, a barrel base plate and a fixed cylinder hold a guide shaft therebetween, and thus bearings of the guide shaft are disposed in two components. This reduces the positioning accuracy of the guide shaft, and makes it difficult to advance and retract the lens in the optical axis direction with high accuracy. In the first lens barrel, the guide shaft is not held until the fixed cylinder is incorporated into the barrel base plate, thereby reducing the assembling workability.
Also, in a second conventional lens barrel in Japanese Laid-Open Patent Publication (Kokai) No. 2006-243569, only a barrel base plate holds a guide shaft. However, in the second conventional lens barrel, the guide shaft is placed outside a fixed cylinder, which reduces the strength of a bearing portion of the barrel base plate. This reduces the positioning accuracy of the guide shaft, and makes it difficult to advance and retract the lens in the optical axis direction with high accuracy.